Lithium-based batteries are finding increasing use in automotive vehicles and in other consumer products. And they have been developed with many different electrode and electrolyte compositions and many different structures for the electrodes, separators, electrolytes, and packaging members for the various lithium battery embodiments. Sodium batteries are also being developed for commercial applications.
Some lithium-based batteries employ a lithium metal anode in combination with a suitable solid electrolyte/separator member and a compatible active counter-electrode material. The solid electrolyte member is a glass, glass-ceramic, or ceramic composition which contains mobile lithium cations that are transportable between the lithium metal anode and a compatible cathode in the cyclical discharge and re-charge operations of the battery cell or assembly of cells. Examples of such electrochemical cells include, for example, lithium-LiMO2 (M=Mn, Co, Ni, Al, etc.) cells, lithium-sulfur cells, and lithium-air cells. Some cells with metallic sodium anodes are also being developed with a solid electrolyte/separator formed of a sodium-ion conductive, glass, glass-ceramic, or ceramic composition.
The glass, glass-ceramic, or ceramic compositions must be prepared for conduction of their respective metal ions to and from the adjacent, overlying faces of the metal electrode during the many repeated cycles of the cell. Among desirable compositions for glasses or glass-ceramics for lithium cells are those which comprise lithium sulfides, oxides, or oxysulfides. Among the desirable compositions for ceramics for lithium cells are those which have a perovskite structure or a structure analogous to the NASICON structure (sodium (Na) SuperIonic CONductor); for example, a lithium-containing perovskite group oxide (Li0.67-xLa3xTiO3, LLTO) and a NASICON lithium aluminum titanium phosphate (Li1.3Al0.3Ti1.7(PO)4, LATP), both synthetic materials. But a problem arises with such lithium sulfide, oxysulfide, and oxide-containing glass electrolyte compositions, and glass-ceramics, and ceramics because their interfaces with their corresponding metal-electrode surfaces are not thermodynamically stable and the operation of the cell is degraded.
There remains a need to address the chemical stability problem at the interfaces of some lithium ion-containing or sodium ion-containing solid electrolyte surfaces and their corresponding metal electrode surfaces as the cell experiences repeated discharge and re-charge cycles.